Due to the small nominal sizes for microsystems, in respect to which reference is made to the scale drawing of FIG. 1, bearings of outer wheels, inner wheels or shafts, which all together are designated as “rotors”, have to meet exacting requirements. Particularly for transporting (conveying or driving) non-lubricating media, it is necessary to use very hard and simultaneously corrosion-resistant materials, such as ceramic or hard metal. The application of said materials is useful for all tribologically stressed functional components of a microsystem, to avoid the use of soft or corrosive materials with a continuous or stronger abrasion. Abrasion in bearing portions, particularly having small and miniature dimensions in a millimeter range (mini to micro system), quickly results in a breakdown of the whole system.
Further, in view of such small nominal sizes, production engineering faces difficulties to constantly keep to the required high-precision dimensions. These dimensional accuracies are in a micrometer range, required accuracy being in the range of 1 to 2 μm. Particularly the use of eccentrically operating microsystems, comprising two rotors meshing with each other, so-called micropumps having internal teeth according to the gerotor principle, require a high-precise observation of the eccentricity, said eccentricity being obtained by two eccentrically positioned bearing portions. In addition to their radial offset, said bearings have an axial offset, but are located axially closely to each other. Thus, for principle reasons, the axes are eccentrically offset relative to each other. Said eccentricity requires a precision in micrometer range, said precision being expensive and complex, if not impossible from the production-engineering point of view, when using metal cutting manufacturing methods with a usual housing structure.